Arithmetic unit for determining a target position for a throttle of an internal combustion engine

Abstract

The present invention refers to a map for operation. The map of the invention represents an absolute value TDST of a difference between a first valve opening ratio TAM of a main throttle valve (35) and a second valve opening ratio TAS of a sub-throttle valve (37) plotted against a restriction value TA, which is the smaller of TAM and TAS. A conventional map requires a high precision around a line of TAM=TAS, that is, in the whole area of the map. The map of the invention, on the other hand, requires a high precision only in a specific range of the absolute value TDST, and allows sparse graduations of the map in an area other than the specific range. This effectively reduces data volume of the map and allows quick reference of the map. More specifically, the present invention determines a corresponding single-valve opening ratio TAA of a dual-valve throttle unit according to the first valve opening ratio TAM of the main throttle valve (35) and the second valve opening ratio TAS of the sub-throttle valve (37) by referring to the map. This method can reduce data volume of the map with out lowering the precision of operation.

What is claimed is: 
     
       1. An arithmetic unit for determining a target amount to which an engine operating parameter is to be set based on a map, wherein the target amount stored in the map is based on a first and a second detected engine operating condition and wherein, under a first engine running state, the first and second engine operating conditions are proportionally related and the target amount varies upon a change in either of the first and second engine operating conditions and wherein, when the engine is not operating under the first running state, the target amount is not substantially effected by a change in the first engine operating condition, wherein: the map represents a difference between the first and second engine operating conditions plotted against a range of values, wherein the range of values represents a range of possible values for both the first and second engine operating conditions, to give a deviation between the target amount and the value of one of the first and second engine operating conditions;   wherein the map has a dense-data area in which the difference between the first and second engine operating conditions is densely graduated, the dense-data area being in a range corresponding to the first engine running state;   wherein the arithmetic unit includes: memory for storing the map; and   target amount computing means for referring to the map stored in the memory to determine, when the first and second engine operating conditions are input, the target amount according to the deviation between the target amount and the value of the selected one of the first and second engine operating conditions.     
     
     
       2. An arithmetic unit in accordance with claim 1, wherein the first and second engine operating conditions are expressed as X and Y, respectively, and are symmetrical with respect to a line of X=Y, wherein: the map stored in the memory represents an absolute value of the difference between the first and second engine operating conditions and wherein the smaller of the first and second engine operating conditions is employed as the selected one of the first and second engine operating conditions to give a deviation between the target amount and the smaller of the first and second engine operating conditions.   
     
     
       3. An arithmetic unit in accordance with claim 1, wherein the memory for storing the map comprises a ROM allowing data to be read and output by specifying an address in the ROM. 
     
     
       4. A throttle valve opening amount computing device for determining, by referring to a map, an equivalent single-valve opening amount corresponding to a first valve opening amount of a first throttle valve and a second valve opening amount of a second throttle valve in a dual-valve throttle unit arranged in an intake conduit of an internal combustion engine, wherein: the map represents a difference between the first valve opening amount and the second valve opening amount plotted against values which represent one of the first and second valve opening amounts to give a deviation between the equivalent single-valve opening amount and the values which represent the one valve opening amount,   wherein the map has a dense-data area in which the difference between the first valve opening amount and the second valve opening amount is densely graduated and wherein the dense-data area is located in a range in which the first valve opening amount and the second valve opening amount are proportionally related, wherein the computing device comprises:   memory for storing the map; and   equivalent single-valve opening amount computing means for determining, when the first valve opening amount and the second valve opening amount are input, an equivalent single-valve opening amount corresponding to the deviation and the one valve opening amount obtained by referring to the map stored in the memory.   
     
     
       5. A throttle valve opening amount computing device in accordance with claim 4, wherein the first valve opening amount and the second valve opening amount of the dual-valve throttle unit are interchangeable in operation for determining the equivalent single-valve opening amount, the map representing an absolute value of the difference between the first and second valve opening amounts plotted against values which are selected to represent the smaller of the first and second valve opening amounts to give a deviation between the equivalent single-valve opening amount and the smaller valve opening amount,   the equivalent single-valve opening ratio computing means determining the equivalent single-valve opening amount according to the deviation and the smaller valve opening amount obtained by referring to the map stored in the memory when data of the first valve opening amount and the second valve opening amount are input.   
     
     
       6. A throttle valve opening amount computing device in accordance with claim 4, the computing device further comprising: a first control unit connected to a first sensor for detecting the first valve opening amount and to a second sensor for detecting the second valve opening amount, the first control unit reading the first and second valve opening amounts to control driving conditions of the internal combustion engine; and   a second control unit coupled to the first control unit, the second control unit comprising a ROM for storing the map and the equivalent single-valve opening amount and the second valve opening ratio transmitted from the first control unit.   
     
     
       7. A throttle valve opening amount computing device in accordance with claim 4, the computing device further comprising: output means for outputting the equivalent single-valve opening amount to a gear control unit for controlling a shift of a gear coupled to an output shaft of the internal combustion engine based on a rotating speed of the internal combustion engine and the equivalent single-valve opening amount.   
     
     
       8. A throttle valve opening amount computing device in accordance with claim 4, wherein: the first throttle valve of the dual-valve throttle unit is directly connected to an accelerator pedal; and   the second throttle valve is coupled to a unit for controlling the second valve opening amount based on the first valve opening amount.   
     
     
       9. A method for determining a target amount to which an engine operating parameter is to be set based on a map, wherein the target amount stored in the map is based on a first and a second detected engine operating condition and wherein, under a first engine running state, the first and second engine operating conditions are proportionally related and the target amount varies upon a change in either of the first and second engine operating conditions and wherein, when the engine is not operating under the first running state, the target amount is not substantially effected by a change in the first engine operating condition, the method comprising the steps of: storing a map in a memory, wherein the map represents a difference between the first and second engine operating conditions plotted against values which represent one of the first and second engine operating conditions to give a deviation between the target amount and the one engine operating condition, the map having a dense-data area in which the difference between the first and second engine operating conditions is more densely graduated than in other areas of the map, wherein the dense-data area corresponds to the first engine running state;   applying the map to determine the deviation when the first and second operating conditions are input; and   determining the target amount based on the deviation.   
     
     
       10. A method in accordance with claim 9, wherein one of the first and second engine operating conditions is represented by a value obtained by transforming a coordinate system for a physical amount actually detected, wherein the method further comprising the steps of:   storing the map in a memory to represent a relationship between the two parameters after transformation of the coordinate system;   applying the map to determine the deviation after the coordinate system is transformed for the physical amount actually detected; and   determining the target amount based on the deviation.